The invention concerns an X-ray film holder or "cassette" having a bottom to receive the X-ray film and image intensifying screens placed against the film; a lid to close the holder; as well as a means for pressing the intensifying screens against the film.
One requirement for an X-ray film holder is that the intensifying screens lying in the holder be pressed firmly against the film. In the conventional holders, the bottom and the lid are hinged together. The pressure is exerted when the holder is closed, and an elastic material, such as foam rubber, provides tolerance compensation and a distribution of pressure over the entire surface of the film. In large holders, the bottom of the holder and the lid bend so much during this process, as a result of the great contact pressure resulting from the large surface, that it is impossible to ensure even pressing when this design is used.
An effective measure to avoid this disadvantage would be to provide even pressure over the entire surface by means of atmospheric pressure; in other words to evacuate the holder as disclosed in the German patent application 22 14 613. The seals required for such a holder, however, cannot maintain the vacuum long enough in practical operation. The holders would in each case have to be evacuated shortly before their use, which is troublesome and time-consuming.